<?php
/**
 * Smarty plugin
 *
 * @package    Smarty
 * @subpackage Security
 * @author     Uwe Tews
 */

/*
 * FIXME: Smarty_Security API
 *      - getter and setter instead of public properties would allow cultivating an internal cache properly
 *      - current implementation of isTrustedResourceDir() assumes that Smarty::$template_dir and Smarty::$config_dir are immutable
 *        the cache is killed every time either of the variables change. That means that two distinct Smarty objects with differing
 *        $template_dir or $config_dir should NOT share the same Smarty_Security instance, 
 *        as this would lead to (severe) performance penalty! how should this be handled? 
 */

/**
 * This class does contain the security settings
 */
class Smarty_Security {

	/**
	 * This determines how Smarty handles "<?php ... ?>" tags in templates.
	 * possible values:
	 * <ul>
	 *   <li>Smarty::PHP_PASSTHRU -> echo PHP tags as they are</li>
	 *   <li>Smarty::PHP_QUOTE    -> escape tags as entities</li>
	 *   <li>Smarty::PHP_REMOVE   -> remove php tags</li>
	 *   <li>Smarty::PHP_ALLOW    -> execute php tags</li>
	 * </ul>
	 *
	 * @var integer
	 */
	public $php_handling = Smarty::PHP_PASSTHRU;
	/**
	 * This is the list of template directories that are considered secure.
	 * $template_dir is in this list implicitly.
	 *
	 * @var array
	 */
	public $secure_dir = array();
	/**
	 * This is an array of directories where trusted php scripts reside.
	 * {@link $security} is disabled during their inclusion/execution.
	 *
	 * @var array
	 */
	public $trusted_dir = array();
	/**
	 * List of regular expressions (PCRE) that include trusted URIs
	 *
	 * @var array
	 */
	public $trusted_uri = array();
	/**
	 * This is an array of trusted static classes.
	 *
	 * If empty access to all static classes is allowed.
	 * If set to 'none' none is allowed.
	 *
	 * @var array
	 */
	public $static_classes = array();
	/**
	 * This is an array of trusted PHP functions.
	 *
	 * If empty all functions are allowed.
	 * To disable all PHP functions set $php_functions = null.
	 *
	 * @var array
	 */
	public $php_functions = array(
			'isset',
			'empty',
			'count',
			'sizeof',
			'in_array',
			'is_array',
			'time',
			'nl2br',
	);
	/**
	 * This is an array of trusted PHP modifers.
	 *
	 * If empty all modifiers are allowed.
	 * To disable all modifier set $modifiers = null.
	 *
	 * @var array
	 */
	public $php_modifiers = array(
			'escape',
			'count'
	);
	/**
	 * This is an array of allowed tags.
	 *
	 * If empty no restriction by allowed_tags.
	 *
	 * @var array
	 */
	public $allowed_tags = array();
	/**
	 * This is an array of disabled tags.
	 *
	 * If empty no restriction by disabled_tags.
	 *
	 * @var array
	 */
	public $disabled_tags = array();
	/**
	 * This is an array of allowed modifier plugins.
	 *
	 * If empty no restriction by allowed_modifiers.
	 *
	 * @var array
	 */
	public $allowed_modifiers = array();
	/**
	 * This is an array of disabled modifier plugins.
	 *
	 * If empty no restriction by disabled_modifiers.
	 *
	 * @var array
	 */
	public $disabled_modifiers = array();
	/**
	 * This is an array of trusted streams.
	 *
	 * If empty all streams are allowed.
	 * To disable all streams set $streams = null.
	 *
	 * @var array
	 */
	public $streams = array('file');
	/**
	 * + flag if constants can be accessed from template
	 *
	 * @var boolean
	 */
	public $allow_constants = true;
	/**
	 * + flag if super globals can be accessed from template
	 *
	 * @var boolean
	 */
	public $allow_super_globals = true;

	/**
	 * Cache for $resource_dir lookups
	 *
	 * @var array
	 */
	protected $_resource_dir = null;
	/**
	 * Cache for $template_dir lookups
	 *
	 * @var array
	 */
	protected $_template_dir = null;
	/**
	 * Cache for $config_dir lookups
	 *
	 * @var array
	 */
	protected $_config_dir = null;
	/**
	 * Cache for $secure_dir lookups
	 *
	 * @var array
	 */
	protected $_secure_dir = null;
	/**
	 * Cache for $php_resource_dir lookups
	 *
	 * @var array
	 */
	protected $_php_resource_dir = null;
	/**
	 * Cache for $trusted_dir lookups
	 *
	 * @var array
	 */
	protected $_trusted_dir = null;


	/**
	 * @param Smarty $smarty
	 */
	public function __construct($smarty) {
		$this->smarty = $smarty;
	}

	/**
	 * Check if PHP function is trusted.
	 *
	 * @param string $function_name
	 * @param object $compiler compiler object
	 *
	 * @return boolean true if function is trusted
	 * @throws SmartyCompilerException if php function is not trusted
	 */
	public function isTrustedPhpFunction($function_name, $compiler) {
		if (isset($this->php_functions) && (empty($this->php_functions) || in_array($function_name, $this->php_functions)))
		{
			return true;
		}

		$compiler->trigger_template_error("PHP function '{$function_name}' not allowed by security setting");

		return false; // should not, but who knows what happens to the compiler in the future?
	}

	/**
	 * Check if static class is trusted.
	 *
	 * @param string $class_name
	 * @param object $compiler compiler object
	 *
	 * @return boolean true if class is trusted
	 * @throws SmartyCompilerException if static class is not trusted
	 */
	public function isTrustedStaticClass($class_name, $compiler) {
		if (isset($this->static_classes) && (empty($this->static_classes) || in_array($class_name, $this->static_classes)))
		{
			return true;
		}

		$compiler->trigger_template_error("access to static class '{$class_name}' not allowed by security setting");

		return false; // should not, but who knows what happens to the compiler in the future?
	}

	/**
	 * Check if PHP modifier is trusted.
	 *
	 * @param string $modifier_name
	 * @param object $compiler compiler object
	 *
	 * @return boolean true if modifier is trusted
	 * @throws SmartyCompilerException if modifier is not trusted
	 */
	public function isTrustedPhpModifier($modifier_name, $compiler) {
		if (isset($this->php_modifiers) && (empty($this->php_modifiers) || in_array($modifier_name, $this->php_modifiers)))
		{
			return true;
		}

		$compiler->trigger_template_error("modifier '{$modifier_name}' not allowed by security setting");

		return false; // should not, but who knows what happens to the compiler in the future?
	}

	/**
	 * Check if tag is trusted.
	 *
	 * @param string $tag_name
	 * @param object $compiler compiler object
	 *
	 * @return boolean true if tag is trusted
	 * @throws SmartyCompilerException if modifier is not trusted
	 */
	public function isTrustedTag($tag_name, $compiler) {
		// check for internal always required tags
		if (in_array($tag_name, array(
				'assign',
				'call',
				'private_filter',
				'private_block_plugin',
				'private_function_plugin',
				'private_object_block_function',
				'private_object_function',
				'private_registered_function',
				'private_registered_block',
				'private_special_variable',
				'private_print_expression',
				'private_modifier'
		))
		)
		{
			return true;
		}
		// check security settings
		if (empty($this->allowed_tags))
		{
			if (empty($this->disabled_tags) || !in_array($tag_name, $this->disabled_tags))
			{
				return true;
			}
			else
			{
				$compiler->trigger_template_error("tag '{$tag_name}' disabled by security setting", $compiler->lex->taglineno);
			}
		}
		else if (in_array($tag_name, $this->allowed_tags) && !in_array($tag_name, $this->disabled_tags))
		{
			return true;
		}
		else
		{
			$compiler->trigger_template_error("tag '{$tag_name}' not allowed by security setting", $compiler->lex->taglineno);
		}

		return false; // should not, but who knows what happens to the compiler in the future?
	}

	/**
	 * Check if modifier plugin is trusted.
	 *
	 * @param string $modifier_name
	 * @param object $compiler compiler object
	 *
	 * @return boolean true if tag is trusted
	 * @throws SmartyCompilerException if modifier is not trusted
	 */
	public function isTrustedModifier($modifier_name, $compiler) {
		// check for internal always allowed modifier
		if (in_array($modifier_name, array('default')))
		{
			return true;
		}
		// check security settings
		if (empty($this->allowed_modifiers))
		{
			if (empty($this->disabled_modifiers) || !in_array($modifier_name, $this->disabled_modifiers))
			{
				return true;
			}
			else
			{
				$compiler->trigger_template_error("modifier '{$modifier_name}' disabled by security setting", $compiler->lex->taglineno);
			}
		}
		else if (in_array($modifier_name, $this->allowed_modifiers) && !in_array($modifier_name, $this->disabled_modifiers))
		{
			return true;
		}
		else
		{
			$compiler->trigger_template_error("modifier '{$modifier_name}' not allowed by security setting", $compiler->lex->taglineno);
		}

		return false; // should not, but who knows what happens to the compiler in the future?
	}

	/**
	 * Check if stream is trusted.
	 *
	 * @param string $stream_name
	 *
	 * @return boolean true if stream is trusted
	 * @throws SmartyException if stream is not trusted
	 */
	public function isTrustedStream($stream_name) {
		if (isset($this->streams) && (empty($this->streams) || in_array($stream_name, $this->streams)))
		{
			return true;
		}

		throw new SmartyException("stream '{$stream_name}' not allowed by security setting");
	}

	/**
	 * Check if directory of file resource is trusted.
	 *
	 * @param string $filepath
	 *
	 * @return boolean true if directory is trusted
	 * @throws SmartyException if directory is not trusted
	 */
	public function isTrustedResourceDir($filepath) {
		$_template = false;
		$_config = false;
		$_secure = false;

		$_template_dir = $this->smarty->getTemplateDir();
		$_config_dir = $this->smarty->getConfigDir();

		// check if index is outdated
		if ((!$this->_template_dir || $this->_template_dir !== $_template_dir) || (!$this->_config_dir || $this->_config_dir !== $_config_dir) || (!empty($this->secure_dir) && (!$this->_secure_dir || $this->_secure_dir !== $this->secure_dir))
		)
		{
			$this->_resource_dir = array();
			$_template = true;
			$_config = true;
			$_secure = !empty($this->secure_dir);
		}

		// rebuild template dir index
		if ($_template)
		{
			$this->_template_dir = $_template_dir;
			foreach ($_template_dir as $directory)
			{
				$directory = realpath($directory);
				$this->_resource_dir[$directory] = true;
			}
		}

		// rebuild config dir index
		if ($_config)
		{
			$this->_config_dir = $_config_dir;
			foreach ($_config_dir as $directory)
			{
				$directory = realpath($directory);
				$this->_resource_dir[$directory] = true;
			}
		}

		// rebuild secure dir index
		if ($_secure)
		{
			$this->_secure_dir = $this->secure_dir;
			foreach ((array)$this->secure_dir as $directory)
			{
				$directory = realpath($directory);
				$this->_resource_dir[$directory] = true;
			}
		}

		$_filepath = realpath($filepath);
		$directory = dirname($_filepath);
		$_directory = array();
		while (true)
		{
			// remember the directory to add it to _resource_dir in case we're successful
			$_directory[$directory] = true;
			// test if the directory is trusted
			if (isset($this->_resource_dir[$directory]))
			{
				// merge sub directories of current $directory into _resource_dir to speed up subsequent lookups
				$this->_resource_dir = array_merge($this->_resource_dir, $_directory);

				return true;
			}
			// abort if we've reached root
			if (($pos = strrpos($directory, DS)) === false || !isset($directory[1]))
			{
				break;
			}
			// bubble up one level
			$directory = substr($directory, 0, $pos);
		}

		// give up
		throw new SmartyException("directory '{$_filepath}' not allowed by security setting");
	}

	/**
	 * Check if URI (e.g. {fetch} or {html_image}) is trusted
	 *
	 * To simplify things, isTrustedUri() resolves all input to "{$PROTOCOL}://{$HOSTNAME}".
	 * So "http://username:password@hello.world.example.org:8080/some-path?some=query-string"
	 * is reduced to "http://hello.world.example.org" prior to applying the patters from {@link $trusted_uri}.
	 *
	 * @param string $uri
	 *
	 * @return boolean true if URI is trusted
	 * @throws SmartyException if URI is not trusted
	 * @uses $trusted_uri for list of patterns to match against $uri
	 */
	public function isTrustedUri($uri) {
		$_uri = parse_url($uri);
		if (!empty($_uri['scheme']) && !empty($_uri['host']))
		{
			$_uri = $_uri['scheme'] . '://' . $_uri['host'];
			foreach ($this->trusted_uri as $pattern)
			{
				if (preg_match($pattern, $_uri))
				{
					return true;
				}
			}
		}

		throw new SmartyException("URI '{$uri}' not allowed by security setting");
	}

	/**
	 * Check if directory of file resource is trusted.
	 *
	 * @param string $filepath
	 *
	 * @return boolean true if directory is trusted
	 * @throws SmartyException if PHP directory is not trusted
	 */
	public function isTrustedPHPDir($filepath) {
		if (empty($this->trusted_dir))
		{
			throw new SmartyException("directory '{$filepath}' not allowed by security setting (no trusted_dir specified)");
		}

		// check if index is outdated
		if (!$this->_trusted_dir || $this->_trusted_dir !== $this->trusted_dir)
		{
			$this->_php_resource_dir = array();

			$this->_trusted_dir = $this->trusted_dir;
			foreach ((array)$this->trusted_dir as $directory)
			{
				$directory = realpath($directory);
				$this->_php_resource_dir[$directory] = true;
			}
		}

		$_filepath = realpath($filepath);
		$directory = dirname($_filepath);
		$_directory = array();
		while (true)
		{
			// remember the directory to add it to _resource_dir in case we're successful
			$_directory[] = $directory;
			// test if the directory is trusted
			if (isset($this->_php_resource_dir[$directory]))
			{
				// merge sub directories of current $directory into _resource_dir to speed up subsequent lookups
				$this->_php_resource_dir = array_merge($this->_php_resource_dir, $_directory);

				return true;
			}
			// abort if we've reached root
			if (($pos = strrpos($directory, DS)) === false || !isset($directory[2]))
			{
				break;
			}
			// bubble up one level
			$directory = substr($directory, 0, $pos);
		}

		throw new SmartyException("directory '{$_filepath}' not allowed by security setting");
	}

}

?>
